The Physiology Course is an intense, challenging, 6 week laboratory course for a class of 36 graduate students, postdoctoral fellows and established investigators who desire to learn the methods and research strategies used to study physiology at the cellular and molecular levels. This is not a routine laboratory course. Instead, we offer approaches that are widely applicable in cellular and molecular biology but potentially intimidating. Through extensive hands on experiments under the close supervision of a large faculty, students learn how to analyze second messengers biochemically and in live cells, reconstitute events in the cell cycle in vitro, crystallize proteins, trace a polypeptide chain through an electron density map, use transient state kinetics, optimize the performance of a videomicroscope, and hunt for crazy mutants in yeast. We also offer stimulating lectures, journal clubs and discussion groups where students can explore in depth the rationale for various experimental approaches with the instructors. Students use state of the an equipment (valued at more than $2 million) provided on loan by various manufacturers. Students chose to work in four of the following six laboratories for periods of 10 days: (1) Microtubule dynamics studied by videomicroscopy and in vitro reconstitution with Ted Salmon and Andrew Murray; (2) Mechanisms of cytoskeletal proteins analyzed by kinetic methods with Tom Pollard and Ed Taylor, (3) Yeast genetics and molecular biology with Rob Jensen and Roy Parker, (4) Macromolecular structure analyzed by x-ray diffraction and electron microscopy with Cindy Stauffacher and Murray Stewart; (5) Cell cycle and nuclear assembly in vitro with Katherine Swensen and Katherine Wilson; and (6) Second messengers and signal transduction with Bill Busa. Some of these sections will highlight the diversity of marine specimens available at Woods Hole and their virtues as experimental systems for modern biology. Interested students may apply for postcourse research.